[BUG] git-gui blame: "Show History Context" is broken

Git-gui as shipped with todays git.git master is a bit broken:

in git.git master (v1.7.0-29-g6d81630), try running:

    $ git gui blame xdiff-interface.h

Then select first line 'd9ea d9ea   1 #ifndef XDIFF_INTERFACE_H', right
click to popup context menu, select "Show History Context" -->

--> git gui errors with:

    "Error: couldn't change working directory to "": no ...


Thanks,
Kirill